The epithelium is the first line of defense against a variety of pathogens. Epithelial cells produce low molecular weight antimicrobial peptides, antibacterial enzymes, and antiproteases. However, optimal methods of specifically targeting therapeutic molecules to epithelial cells have been lacking in the art. There is a continuing need in the art for methods of providing therapeutic agents to respiratory epithelia cells in diseases such as cyptic fibrosis, asthma, and emphysema, and to intestinal epithelial cells, for example, in inflammatory bowel diseases.